Examples of combustible waste include tyres, furniture, carpets, wood refuse, garden waste, kitchen waste, paper sludge, biomass, petcoke, sewage sludge and bleaching earth.
From EP-1200778, the contents of which is hereby invoked as being part of the present application, is known a method as well as an apparatus of the aforementioned kind according to which the waste is burned in the separate compartment subject to simultaneous supply of hot air coming preferably from the clinker cooler. The exhaust gases formed during incineration are directed from the compartment into the preheater where they are utilized for heating the cement raw meal. In practice, this method and apparatus have proven to be particularly suitable for the incineration of waste, providing a significant heat contribution which has improved the total operating economics of the plant. However, it has also been ascertained that the NOx emission from this known apparatus may be at a high level given that in the compartment there is no reduction of the NOx which is formed in the kiln during the burning of cement clinker. In addition, the amount of fuel, which is introduced into a possible NOx reducing zone in the calciner, and being available for the reduction of the NOx vented from the kiln, is reduced, hence this kiln NOx in doing so is reduced less effectively.